SMARCA4-deficient dedifferentiated endometrioid carcinoma

Background: SMARCA4-deficient, dedifferentiated endometrioid carcinoma （SDDEC）with distinct rhabdoid cells is a rare uterine malignancy. A 58-year-old case was presented.The undifferentiated carcinoma component was 90% and filled with rhabdoid cells, which is easily mistaken for SMARCA4-deficient undifferentiated uterine sarcoma (SDUS). In contrast to earlier findings, the undifferentiated carcinoma component's MMR status was distinct from that of endometrioid adenocarcinoma. We discuss the clinicopathological characteristics, the clinical course of treatment, and a literature review. Case presentation The patient was 58 years old and admitted with postmenopausal vaginal bleeding and lower abdominal pain. An MRI revealed a significant uterine tumor and an ambiguous sigmoid colon boundary. A cytoreductive procedure was carried out. A CT scan performed two weeks after surgery revealed liver metastases and new, enlarged lymph nodes in the mediastinum. Anti-PD-1 immunotherapy was tested. One month after the procedure, the patient died. The final pathological diagnosis was SMARCA4-deficient dedifferentiated endometrial carcinoma. SMARCA4 loss was only present in the undifferentiated carcinoma, which manifested as MMRp. As well, the endometrioid adenocarcinoma component had intact SMARCB1 and SMARCA4 expression, which manifested as MMRd. Conclusion: Mutations in SMARCA4 result in clinically hyperaggressive malignant rhabdomyoblastic tumors.Future research will focus heavily on multimodal therapy, which combines surgical tumor removal, postoperative chemotherapy, radiation, and immunotherapy, for SDDEC.